Methods and apparatus for a stent having an expandable web structure

ABSTRACT

The present invention provides a stent comprising a tubular flexible body having a wall with a web structure that is expandable from a contracted delivery configuration to deployed configuration. The web structure comprises a plurality of neighboring web patterns, where each web patterns is composed of adjoining webs, and the web patterns are interconnected. Each adjoining web comprises a central section interposed between two lateral sections to form concave or convex configurations.

REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part application ofU.S. patent application Ser. No. 09/582,318, filed Jun. 23, 2000, whichclaims the benefit of the filing date of International ApplicationPCT/EP99/06456, filed Sep. 2, 1999, which claims priority from Germanapplication 19840645.2, filed Sep. 5, 1998.

FIELD OF THE INVENTION

[0002] The present invention relates to stents. More particularly, thepresent invention relates to stents having a web structure configured toexpand from a contracted delivery configuration to an expanded deployedconfiguration.

BACKGROUND OF THE INVENTION

[0003] Various stent designs are known in the art. These stents formvascular prostheses fabricated from biocompatible materials. Stents aretypically used to expand and maintain patency of hollow vessels, such asblood vessels or other body orifices. To this end, the stent is oftenplaced into a hollow vessel of a patient's body in a contracted deliveryconfiguration and is subsequently expanded by suitable means, such as bya balloon catheter, to a deployed configuration.

[0004] A stent often comprises a stent body that is expandable from thecontracted to the deployed configuration. A common drawback of such astent is that the stent decreases in length, or foreshortens, along itslongitudinal axis as it expands. Such shortening is undesirable because,in the deployed configuration, the stent may not span the entire areainside a vessel or orifice that requires expansion and/or support.

[0005] It therefore would be desirable to provide a stent thatexperiences reduced foreshortening during deployment.

[0006] It also would be desirable to provide a stent that is flexible,even in the contracted delivery configuration.

[0007] It would be desirable to provide a stent having radial stiffnessin the expanded deployed configuration sufficient to maintain vesselpatency in a stenosed vessel.

SUMMARY OF THE INVENTION

[0008] In view of the foregoing, it is an object of the presentinvention to provide a stent that experiences reduced foreshorteningduring deployment.

[0009] It is another object to provide a stent that is flexible, even inthe contracted delivery configuration.

[0010] It is also an object to provide a stent having radial stiffnessin the expanded deployed configuration sufficient to maintain vesselpatency in a stenosed vessel.

[0011] These and other objects of the present invention are accomplishedby providing a stent having a tubular body whose wall has a webstructure configured to expand from a contracted delivery configurationto an expanded deployed configuration. The web structure comprises aplurality of neighboring web patterns having adjoining webs. Each webhas three sections: a central section arranged substantially parallel tothe longitudinal axis in the contracted delivery configuration, and twolateral sections coupled to the ends of the central section. The anglesbetween the lateral sections and the central section increase duringexpansion, thereby reducing or substantially eliminating length decreaseof the stent due to expansion, while increasing a radial stiffness ofthe stent.

[0012] Preferably, each of the three sections of each web issubstantially straight, the lateral sections preferably define obtuseangles with the central section, and the three sections are arrangedrelative to one another to form a concave or convex structure. Whencontracted to its delivery configuration, the webs resemble stacked ornested bowls or plates. This configuration provides a compact deliveryprofile, as the webs are packed against one another to form web patternsresembling rows of stacked plates.

[0013] Neighboring web patterns are preferably connected to one anotherby connection elements preferably formed as straight sections. In apreferred embodiment, the connection elements extend between adjacentweb patterns from the points of interconnection between neighboring webswithin a given web pattern.

[0014] The orientation of connection elements between a pair ofneighboring web patterns preferably is the same for all connectionelements disposed between the pair. However, the orientation ofconnection elements alternates between neighboring pairs of neighboringweb patterns. Thus, a stent illustratively flattened and viewed as aplane provides an alternating orientation of connection elements betweenthe neighboring pairs: first upwards, then downwards, then upwards, etc.

[0015] As will be apparent to one of skill in the art, positioning,distribution density, and thickness of connection elements and adjoiningwebs may be varied to provide stents exhibiting characteristics tailoredto specific applications. Applications may include, for example, use inthe coronary or peripheral (e.g. renal) arteries. Positioning, density,and thickness may even vary along the length of an individual stent inorder to vary flexibility and radial stiffness characteristics along thelength of the stent.

[0016] Stents of the present invention preferably are flexible in thedelivery configuration. Such flexibility beneficially increases aclinician's ability to guide the stent to a target site within apatient's vessel. Furthermore, stents of the present inventionpreferably exhibit high radial stiffness in the deployed configuration.Implanted stents therefore are capable of withstanding compressiveforces applied by a vessel wall and maintain vessel patency. The webstructure described hereinabove provides the desired combination offlexibility in the delivery configuration and radial stiffness in thedeployed configuration. The combination further may be achieved, forexample, by providing a stent having increased wall thickness in a firstportion of the stent and decreased wall thickness with fewer connectionelements in an adjacent portion or portions of the stent.

[0017] Depending on the material of fabrication, a stent of the presentinvention may be either self-expanding or expandable by other suitablemeans, for example, using a balloon catheter. Self-expanding embodimentspreferably are fabricated from a superelastic material, such as anickel-titanium alloy. Regardless of the expansion mechanism used, thebeneficial aspects of the present invention are maintained: reducedshortening upon expansion, high radial stiffness, and a high degree offlexibility.

[0018] Methods of using stents in accordance with the present inventionare also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects and advantages of the presentinvention will be apparent upon consideration of the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich like reference numerals refer to like parts throughout, and inwhich:

[0020]FIG. 1 is a schematic isometric view illustrating the basicstructure of a stent according to the present invention;

[0021]FIG. 2 is a schematic view illustrating a web structure of a wallof the stent of FIG. 1 in a contracted delivery configuration;

[0022]FIG. 3 is a schematic view illustrating the web structure of thestent of FIG. 1 in an expanded deployed configuration;

[0023]FIG. 4 is an enlarged schematic view of the web structure in thedelivery configuration;

[0024]FIG. 5 is a schematic view of an alternative web structure of thestent of FIG. 1 having transition sections and shown in anas-manufactured configuration;

[0025]FIGS. 6A and 6B are, respectively, a schematic view and detailedview of an alternative embodiment of the web structure of FIG. 5;

[0026] FIGS. 7A-7D are, respectively, schematic and detailed views ofanother alternative embodiment of the web structure of the stent of thepresent invention, and a cross-sectional view of the stent;

[0027]FIGS. 8A and 8B are views further alternative embodiments of thestent of the present application having different interconnectionpatterns;

[0028]FIGS. 9A and 9B are, respectively, a schematic and detailed viewof yet another alternative embodiment of the web structure of FIG. 5;and

[0029] FIGS. 10A-10D illustrate a method of deploying a balloonexpandable embodiment of a stent constructed in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0030] Referring to FIG. 1, stent 1 comprises tubular flexible body 2.Tubular flexible body 2, in turn, comprises wall 3 having a webstructure, as described hereinbelow with respect to FIGS. 2-9. Stent 1and its web structure are expandable from a contracted deliveryconfiguration to an expanded deployed configuration. Depending on thematerial of fabrication, stent 1 may be either self-expanding orexpandable using a balloon catheter. If self-expanding, the webstructure is preferably fabricated from a superelastic material, such asa nickel-titanium alloy. Furthermore, stent 1 preferably is fabricatedfrom biocompatible or biodegradable materials. It also may be radiopaqueto facilitate delivery, and it may comprise an external coating C thatretards thrombus formation or restenosis within a vessel. The coatingalternatively may deliver therapeutic agents into the patient's bloodstream.

[0031] With reference to FIGS. 2-4, a first embodiment of the webstructure of stent 1 is described. In FIGS. 2-4, wall 3 of body 2 ofstent 1 is shown flattened into a plane for illustrative purposes. FIG.2 shows web structure 4 in a contracted delivery configuration, withline L indicating the longitudinal axis of the stent. Web structure 4comprises neighboring web patterns 5 and 6 arranged in alternating,side-by-side fashion. Thus, the web patterns seen in FIG. 2 are arrangedin the sequence 5, 6, 5, 6, 5, etc.

[0032]FIG. 2 illustrates that web patterns 5 comprise adjoining webs 9(concave up in FIG. 2), while web patterns 6 comprise adjoining webs 10(convex up in FIG. 2). Each of these webs has a concave or convex shaperesulting in a stacked plate- or bowl-like appearance when the stent iscontracted to its delivery configuration. Webs 9 of web patterns 5 arerotated 180 degrees with respect to webs 10 of web patterns 6, i.e.,alternating concave and convex shapes. The structure of webs 9 and 10 isdescribed in greater detail hereinbelow with respect to FIG. 4.

[0033] Neighboring web patterns 5 and 6 are interconnected by connectionelements 7 and 8. A plurality of connection elements 7 and 8 areprovided longitudinally between each pair of web patterns 5 and 6.Multiple connection elements 7 and 8 are disposed in the circumferentialdirection between adjacent webs 5 and 6. The position, distributiondensity, and thickness of these pluralities of connection elements maybe varied to suit specific applications in accordance with the presentinvention.

[0034] Connection elements 7 and 8 exhibit opposing orientation.However, all connection elements 7 have the same orientation that, asseen in FIG. 2, extends from the left side, bottom, to the right side,top. Likewise, all connection elements 8 have the same orientation thatextends from the left side, top, to the right side, bottom. Connectionelements 7 and 8 alternate between web patterns 5 and 6, as depicted inFIG. 2.

[0035]FIG. 3 illustrates the expanded deployed configuration of stent 1,again with reference to a portion of web structure 4. When stent 1 is inthe expanded deployed configuration, web structure 4 provides stent 1with high radial stiffness. This stiffness enables stent 1 to remain inthe expanded configuration while, for example, under radial stress.Stent 1 may experience application of radial stress when, for example,implanted into a hollow vessel in the area of a stenosis.

[0036]FIG. 4 is an enlarged view of web structure 4 detailing a portionof the web structure disposed in the contracted delivery configurationof FIG. 2. FIG. 4 illustrates that each of webs 9 of web pattern 5comprises three sections 9 a, 9 b and 9 c, and each of webs 10 of webpattern 6 comprises three sections 10 a, 10 b and 10 c. Preferably, eachindividual section 9 a, 9 b, 9 c, 10 a, 10 b and 10 c, has a straightconfiguration.

[0037] Each web 9 has a central section 9 b connected to lateralsections 9 a and 9 c, thus forming the previously mentioned bowl- orplate-like configuration. Sections 9 a and 9 b enclose obtuse angle a.Likewise, central section 9 b and lateral section 9 c enclose obtuseangle β. Sections 10 a-10 c of each web 10 of each web pattern 6 aresimilarly configured, but are rotated 180 degrees with respect tocorresponding webs 9. Where two sections 9 a or 9 c, or 10 a or 10 cadjoin one another, third angle γ is formed (this angle is zero wherethe stent is in the fully contracted position, as shown in FIG. 4).

[0038] Preferably, central sections 9 b and 10 b are substantiallyaligned with the longitudinal axis L of the tubular stent when the stentis in the contracted delivery configuration. The angles between thesections of each web increase in magnitude during expansion to thedeployed configuration, except that angle γ, which is initially zero oracute, approaches a right angle after deployment of the stent. Thisincrease provides high radial stiffness with reduced shortening of thestent length during deployment. As will of course be understood by oneof ordinary skill, the number of adjoining webs that span acircumference of the stent preferably is selected corresponding to thevessel diameter in which the stent is intended to be implanted.

[0039]FIG. 4 illustrates that, with stent 1 disposed in the contracteddelivery configuration, webs 9 adjoin each other in an alternatingfashion and are each arranged like plates stacked into one another, asare adjoining webs 10. FIG. 4 further illustrates that the configurationof the sections of each web applies to all of the webs which jointlyform web structure 4 of wall 3 of tubular body 2 of stent 1. Webs 9 areinterconnected within each web pattern 5 via rounded connection sections12, of which one connection section 12 is representatively labeled. Webs10 of each neighboring web pattern 6 are similarly configured.

[0040]FIG. 4 also once again demonstrates the arrangement of connectionelements 7 and 8. Connection elements 7, between a web pattern 5 and aneighboring web pattern 6, are disposed obliquely relative to thelongitudinal axis L of the stent with an orientation A, which is thesame for all connection elements 7. Orientation A is illustrated by astraight line that generally extends from the left side, bottom, to theright side, top of FIG. 4. Likewise, the orientation of all connectionelements 8 is illustrated by line B that generally extends from the leftside, top, to the right side, bottom of FIG. 4. Thus, an alternating A,B, A, B, etc., orientation is obtained over the entirety of webstructure 4 for connection elements between neighboring web patterns.

[0041] Connection elements 7 and 8 are each configured as a straightsection that passes into a connection section 11 of web pattern 5 andinto a connection section 11′ of web pattern 6. This is illustrativelyshown in FIG. 4 with a connection element 7 extending betweenneighboring connection sections 11 and 11′, respectively. It should beunderstood that this represents a general case for all connectionelements 7 and 8.

[0042] Since each web consists of three interconnected sections thatform angles α and β with respect to one another, which angles arepreferably obtuse in the delivery configuration, expansion to thedeployed configuration of FIG. 3 increases the magnitude of angles α andβ. This angular increase beneficially provides increased radialstiffness in the expanded configuration. Thus, stent 1 may be flexiblein the contracted delivery configuration to facilitate delivery throughtortuous anatomy, and also may exhibit sufficient radial stiffness inthe expanded configuration to ensure vessel patency, even when deployedin an area of stenosis. The increase in angular magnitude also reducesand may even substantially eliminate length decrease of the stent due toexpansion, thereby decreasing a likelihood that stent 1 will notcompletely span a target site within a patient's vessel post-deployment.

[0043] The stent of FIG. 4 is particularly well-suited for use as aself-expanding stent when manufactured, for example, from a shape memoryalloy such as nickel-titanium. In this case, web patterns 5 and 6preferably are formed by laser-cutting a tubular member, whereinadjacent webs 9 and 10 are formed using slit-type cuts. Only the areascircumferentially located between connection members 7 and 8 (shadedarea D in FIG. 4) require removal of areas of the tubular member. Theseareas also may be removed from the tubular member using laser cuttingtechniques.

[0044] Referring now to FIG. 5, an alternative embodiment of the webstructure of stent 1 is described. FIG. 5 shows the alternative webstructure in an as-manufactured configuration. The basic pattern of theembodiment of FIG. 5 corresponds to that of the embodiment of FIGS. 2-4.Thus, this alternative embodiment also relates to a stent having atubular flexible body with a wall having a web structure configured toexpand from a contracted delivery configuration to the deployedconfiguration.

[0045] Likewise, the web structure again comprises a plurality ofneighboring web patterns, of which two are illustratively labeled inFIG. 5 as web patterns 5 and 6. Web patterns 5 and 6 are again providedwith adjoining webs 9 and 10, respectively. Each of webs 9 and 10 issubdivided into three sections, and reference is made to the discussionprovided hereinabove, particularly with respect to FIG. 4. As will ofcourse be understood by one of skill in the art, the stent of FIG. 5will have a smaller diameter when contracted (or crimped) for delivery,and may have a larger diameter than illustrated in FIG. 5 when deployed(or expanded) in a vessel.

[0046] The embodiment of FIG. 5 differs from the previous embodiment bythe absence of connection elements between web patterns. In FIG. 5, webpatterns are interconnected to neighboring web patterns by transitionsections 13, as shown by integral transition section 13 disposed betweensections 9 c and 10 c. Symmetric, inverted web patterns are therebyobtained in the region of transition sections 13. To enhance stiffness,transition sections 13 preferably have a width greater than twice thewidth of webs 9 or 10.

[0047] As seen in FIG. 5, every third neighboring pair of webs 9 and 10is joined by an integral transition section 13. As will be clear tothose of skill in the art, the size and spacing of transition sections13 may be altered in accordance with the principles of the presentinvention.

[0048] An advantage of the web structure of FIG. 5 is that it providesstent 1 with compact construction coupled with a high degree offlexibility in the delivery configuration and high load-bearingcapabilities in the deployed configuration. Furthermore, FIG. 5illustrates that, as with connection elements 7 and 8 of FIG. 4,transition sections 13 have an alternating orientation and are disposedobliquely relative to the longitudinal axis of the stent (shown byreference line L). FIG. 5 also illustrates that, especially in thedeployed configuration, an H-like configuration of transition sections13 with adjoining web sections is obtained.

[0049] The stent of FIG. 5 is well-suited for use as aballoon-expandable stent, and may be manufactured from stainless steelalloys. Unlike the stent of FIG. 4, which is formed in the contracteddelivery configuration, the stent of FIG. 5 preferably is formed in apartially deployed configuration by removing the shaded areas D′ betweenwebs 9 and 10 using laser-cutting or chemical etching techniques. Inthis case, central sections 9 b and 10 b are substantially aligned withthe longitudinal axis L of the stent when the stent is crimped onto thedilatation balloon of a delivery system.

[0050] Referring now to FIGS. 6 and 7, alternative embodiments of theweb structure of FIG. 5 are described. These web structures differ fromthe embodiment of FIG. 5 in the spacing of the transition sections. Webstructure 15 of FIGS. 6A and 6B provides a spacing of transitionsections 16 suited for use in the coronary arteries. FIG. 6A shows theoverall arrangement, while FIG. 6B provides a detail view of region A ofFIG. 6A. Other arrangements and spacings will be apparent to those ofskill in the art and fall within the scope of the present invention.

[0051] Web structure 17 of FIGS. 7A-7D provides stent 1 with a variablewall thickness and a distribution density or spacing of transitionsections 16 suited for use in the renal arteries. FIG. 7A shows thearrangement of web structure 17 along the length of stent 1, anddemonstrates the spacing of transition sections 18. FIGS. 7C and 7Dprovide detail views of regions A and B, respectively, of FIG. 7A,showing how the spacing and shape of the webs that make up web structure17 change as stent 1 changes along its length. In particular, asdepicted (not to scale) in FIG. 7D, stent 1 has first thickness t₁ forfirst length L₁ and second thickness t₂ for second length L₂.

[0052] The variation in thickness, rigidity and number of struts of theweb along the length of the stent of FIGS. 7A-7D facilitates use of thestent in the renal arteries. For example, the thicker region L₁ includesmore closely spaced and sturdier struts to provide a high degree ofsupport in the ostial region, while the thinner region L₂ includes fewerand thinner struts to provide greater flexibility to enter the renalarteries. For such intended applications, region L₁ preferably has alength of about 6-8 mm and a nominal thickness t₁ of 0.21 mm, and regionL₂ has a length of about 5 mm and a nominal thickness t₂ of about 0.15mm.

[0053] As depicted in FIGS. 7A-7D, the reduction in wall thickness mayoccur as a step along the exterior of the stent, such as may be obtainedby grinding or chemical etching. One of ordinary skill in the art willappreciate, however, that the variation in thickness may occur graduallyalong the length of the stent, and that the reduction in wall thicknesscould be achieved by alternatively removing material from the interiorsurface of the stent, or both the exterior and interior surfaces of thestent.

[0054] In FIGS. 8A and 8B, additional embodiments of web structures ofthe present invention, similar to FIG. 5, are described, in which line Lindicates the direction of the longitudinal axis of the stent. In FIG.5, every third neighboring pair of webs is joined by an integraltransition section 13, and no set of struts 9 a-9 c or 10 a-10 cdirectly joins two transition sections 13. In the embodiment of FIG. 8A,however, integral transition sections 20 are arranged in a pattern sothat the transition sections span either four or three adjacent webs.For example, the portion indicated as 22 in FIG. BA includes threeconsecutively joined transition sections, spanning four webs. In thecircumferential direction, portion 22 alternates with the portionindicated at 24, which includes two consecutive transition sections,spanning three webs.

[0055] By comparison, the web pattern depicted in FIG. 8B includes onlyportions 24 that repeat around the circumference of the stent, and spanonly three webs at a time. As will be apparent to one of ordinary skill,other arrangements of integral transition regions 13 may be employed,and may be selected on an empirical basis to provide any desired degreeof flexibility and trackability in the contracted deliveryconfiguration, and suitable radial strength in the deployedconfiguration.

[0056] Referring now to FIGS. 9A and 9B, a further alternativeembodiment of the stent of FIG. 8B is described, in which the transitionsections are formed with reduced thickness. Web structure 26 comprisestransition sections 27 disposed between neighboring web patterns.Sections 27 are thinner and comprise less material than transitionsections 20 of the embodiment of FIG. 8B, thereby enhancing flexibilitywithout significant reduction in radial stiffness.

[0057] Referring now to FIGS. 10A-10D, a method of using a balloonexpandable embodiment of stent 1 is provided. Stent 1 is disposed in acontracted delivery configuration over balloon 30 of balloon catheter32. As seen in FIG. 10A, the distal end of catheter 32 is delivered to atarget site T within a patient's vessel V using, for example, well-knownpercutaneous techniques. Stent 1 or portions of catheter 32 may beradiopaque to facilitate positioning within the vessel. Target site Tmay, for example, comprise a stenosed region of vessel V at which anangioplasty procedure has been conducted.

[0058] In FIG. 10B, balloon 30 is inflated to expand stent 1 to thedeployed configuration in which it contacts the wall of vessel V attarget site T. Notably, the web pattern of stent 1 described hereinaboveminimizes a length decrease of stent 1 during expansion, therebyensuring that stent 1 covers all of target site T. Balloon 30 is thendeflated, as seen in FIG. 10C, and balloon catheter 32 is removed fromvessel V, as seen in FIG. 10D.

[0059] Stent 1 is left in place within the vessel. Its web structureprovides radial stiffness that maintains stent 1 in the expandedconfiguration and minimizes restenosis. Stent 1 may also compriseexternal coating C configured to retard restenosis or thrombosisformation around the stent. Coating C may alternatively delivertherapeutic agents into the patient's blood stream.

[0060] Although preferred illustrative embodiments of the presentinvention are described hereinabove, it will be evident to one skilledin the art that various changes and modifications may be made thereinwithout departing from the invention. It is intended in the appendedclaims to cover all such changes and modifications that fall within thetrue spirit and scope of the invention.

What is claimed is:
 1. A stent comprising: a tubular body with a wallhaving a web structure configured to expand from a contracted deliveryconfiguration to an expanded deployed configuration, the web structurecomprising a plurality of interconnected, neighboring web patterns, eachweb pattern having a plurality of adjoining webs, each adjoining webcomprising a central section interposed between first and second lateralsections, wherein the central section is substantially parallel to alongitudinal axis of the stent when in a contracted deliveryconfiguration, each of the first lateral sections joins the centralsection at a first angle, each of the second lateral sections joins thecentral section at a second angle, and adjacent ones of the neighboringweb patterns having alternating concavity.
 2. The stent of claim 1,wherein each of the three sections of each adjoining web is straight. 3.The stent of claim 1, wherein the first angle comprises a first obtuseangle, and wherein the second angle comprises a second obtuse angle. 4.The stent of claim 1, wherein the first angle is equal to the secondangle.
 5. The stent of claim 1, wherein each adjoining web has abowl-like appearance.
 6. The stent of claim 1 further comprising aplurality of connection elements configured to interconnect theplurality of web patterns.
 7. The stent of claim 6, wherein each of theplurality of connection elements comprises a straight section.
 8. Thestent of claim 6, wherein each web pattern comprises a plurality ofconnection sections, the connection elements configured to coupleneighboring connection sections together to interconnect the pluralityof web patterns.
 9. The stent of claim 6, wherein the plurality ofconnection elements comprise a first plurality of connection elementsdisposed in a first orientation and a second plurality of connectionelements disposed in a second orientation.
 10. The stent of claim 9,wherein the first and second plurality of connection elements,respectively, are disposed between neighboring web patterns in analternating arrangement.
 11. The stent of claim 1 further comprising aplurality of transition sections configured to interconnect neighboringweb patterns.
 12. The stent of claim 11, wherein the transition sectionscomprise extensions of neighboring adjoining webs.
 13. The stent ofclaim 1, wherein the web structure is fabricated from a superelasticmaterial.
 14. The stent of claim 1, wherein the stent is fabricated froma biocompatible or biodegradable material.
 15. The stent of claim 1,wherein the tubular body is flexible in the contracted deliveryconfiguration.
 16. The stent of claim 1, wherein the web structure isconfigured to self-expand from the contracted delivery configuration tothe expanded deployed configuration.
 17. The stent of claim 1, whereinthe web structure is configured to expand by application of pressure toan interior surface of the stent from the contracted deliveryconfiguration to the expanded deployed configuration.
 18. The stent ofclaim 1, wherein a third angle is formed where adjoining web patternsare joined, the third angle being acute in the contracted deliveryconfiguration.
 19. The stent of claim 18, wherein the third angleincreases in magnitude when the web structure deploys from thecontracted delivery configuration to the expanded deployedconfiguration.
 20. The stent of claim 18, wherein the third angleapproaches a right angle after deployment of the stent.
 21. The stent ofclaim 1, wherein the number of adjoining webs that span a circumferenceof the stent is selected corresponding to a vessel diameter in which thestent is to be implanted.
 22. The stent of claim 12 wherein eachtransition section has a transition width having a width greater thantwice the width of the central section.
 23. The stent of claim 1 furthercomprising, a plurality of connection sections configured to adjoin theadjoining webs.
 24. The stent of claim 1 further comprising an coatingpartially covering the tubular body.
 25. The stent of claim 24 whereinthe coating is configured to retard restenosis.
 26. The stent of claim24, wherein the coating is configured to retard thrombus formationaround the stent.
 27. The stent of claim 24, wherein the coating isconfigured to deliver therapeutic agents to the patient's blood stream.28. The stent of claim 1, wherein a thickness of the wall of the tubularbody changes along a length of the tubular body.
 29. A method forstenting at a target site within a patient's vessel comprising:providing a stent comprising a tubular body with a wall having a webstructure, the web structure comprising a plurality of interconnected,neighboring web patterns, each web pattern having a plurality ofadjoining webs, each adjoining web comprising a central sectionsinterposed between two lateral sections, wherein the central section issubstantially parallel to a longitudinal axis of the stent when in acontracted delivery configuration, and adjacent ones of the neighboringweb patterns having alternating concavity; percutaneously delivering thestent to the target site within the patient's vessel in a contracteddelivery configuration; and deploying the stent to an expanded deployedconfiguration, wherein the stent engages the target site.
 30. The methodof claim 29, wherein each of the first lateral sections joins thecentral section at a first angle and each of the second lateral sectionsjoins the central section at a second angle, and expanding the stentcomprises increasing a magnitude of the first and second angles.
 31. Themethod of claim 30, wherein increasing the magnitude of the anglesincreases a radial stiffness of the stent.
 32. The method of claim 30,wherein increasing the magnitude of the angles maintains a substantiallyconstant length of the stent during expansion.
 33. The method of claim29 wherein deploying the stent to an expanded deployed configurationcomprises using a delivery system to apply a radially-outwardly directedforce against an interior surface of the stent.
 34. The method of claim29 wherein deploying the stent to an expanded configuration comprisesreleasing the stent from a mechanical restraint.
 35. The method of claim29, wherein deploying the stent to an expanded deployed configurationfurther comprises increasing a third angle disposed between adjoiningwebs to substantially a right angle.